# operator==,!=,<,<=,>,>=,<=>(std::chrono::duration)

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< cpp‎ | chrono‎ | duration

template< class Rep1, class Period1, class Rep2, class Period2 > constexpr bool operator==( const std::chrono::duration<Rep1, Period1>& lhs, const std::chrono::duration<Rep2, Period2>& rhs ); | (1) | (since C++11)
template< class Rep1, class Period1, class Rep2, class Period2 > constexpr bool operator!=( const std::chrono::duration<Rep1, Period1>& lhs, const std::chrono::duration<Rep2, Period2>& rhs ); | (2) | (since C++11) (until C++20)
template< class Rep1, class Period1, class Rep2, class Period2 > constexpr bool operator<( const std::chrono::duration<Rep1, Period1>& lhs, const std::chrono::duration<Rep2, Period2>& rhs ); | (3) | (since C++11)
template< class Rep1, class Period1, class Rep2, class Period2 > constexpr bool operator<=( const std::chrono::duration<Rep1, Period1>& lhs, const std::chrono::duration<Rep2, Period2>& rhs ); | (4) | (since C++11)
template< class Rep1, class Period1, class Rep2, class Period2 > constexpr bool operator>( const std::chrono::duration<Rep1, Period1>& lhs, const std::chrono::duration<Rep2, Period2>& rhs ); | (5) | (since C++11)
template< class Rep1, class Period1, class Rep2, class Period2 > constexpr bool operator>=( const std::chrono::duration<Rep1, Period1>& lhs, const std::chrono::duration<Rep2, Period2>& rhs ); | (6) | (since C++11)
template< class Rep1, class Period1, class Rep2, class Period2 > requires std::three_way_comparable<std::common_type_t<Rep1, Rep2>> constexpr auto operator<=>( const std::chrono::duration<Rep1, Period1>& lhs, const std::chrono::duration<Rep2, Period2>& rhs ); | (7) | (since C++20)

Compares two durations. Let `CT` be std::common_type<std::chrono::duration<Rep1, Period1>, std::chrono::duration<Rep2, Period2>>::type:

1,2) Checks if lhs and rhs are equal, i.e. the number of ticks for the type common to both durations are equal.
3-6) Compares lhs to rhs, i.e. compares the number of ticks for the type common to both durations.
7) Compares lhs to rhs, i.e. compares the number of ticks for the type common to both durations. The return type is deduced from CT(lhs).count() <=> CT(rhs).count().

The `!=` operator is synthesized from `operator==`. | (since C++20)

### Parameters

lhs | - | duration on the left-hand side of the operator
rhs | - | duration on the right-hand side of the operator

### Return value

1) CT(lhs).count() == CT(rhs).count()
2) !(lhs == rhs)
3) CT(lhs).count() < CT(rhs).count()
4) !(rhs < lhs)
5) rhs < lhs
6) !(lhs < rhs)
7) CT(lhs).count() <=> CT(rhs).count()

### Example

Run this code

    #include <chrono>
    #include <iostream>

    int main()
    {
        constexpr auto t1 = std::chrono::seconds(2);
        constexpr auto t2 = std::chrono::milliseconds(2000);

        if constexpr (t1 == t2)
            std::cout << t1 << " == " << t2 << '\n';
        else
            std::cout << t1 << " != " << t2 << '\n';

        constexpr auto t3 = std::chrono::seconds(61);
        constexpr auto t4 = std::chrono::minutes(1);

        if constexpr (t3 > t4)
            std::cout << t3 << " > " << t4 << '\n';
        else
            std::cout << t3 << " <= " << t4 << '\n';

        using namespace std::chrono_literals;

        static_assert(1h == 60min);
        static_assert(1min == 60s);
        static_assert(1s == 1'000ms);
        static_assert(1ms == 1'000us);
        static_assert(1us == 1'000ns);
    }

Output:

    2s == 2000ms
    61s > 1min

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